Method and Apparatus for Controlling Downlink HARQ Timing in TDD Environment

ABSTRACT

The present specification relates to a method and an apparatus for controlling downlink HARQ timing. A method for controlling downlink HARQ timing according to an embodiment of the present invention comprises the steps of: configuring, by a base station, different duplex modes for a PCell and an SCell and transmitting the configuration information to a terminal; transmitting, by the base station, a PDSCH in subframe n-k of the SCell; and receiving, by the base station, HARQ response information from the terminal in subframe n of the PCell by applying a set index associated with downlink HARQ timing corresponding to the configuration information, wherein k has a value of 4-13.

PRIORITY CLAIM

This application claims priority to U.S. patent application Ser. No.14/910,798, entitled “Method and Apparatus for Controlling Downlink HARQTiming in TDD Environment”, filed Mar. 30, 2016, which is a 371 ofInternational PCT/KR2014/007372, filed Aug. 8, 2014, and claims priorityto Korean Patent Application No. 10-2013-0094389, filed on Aug. 8, 2013each of which is hereby incorporated by reference in its entirety asthough fully and completely set forth herein.

The claims in the instant application are different than those of theparent application or other related applications. The Applicanttherefore rescinds any disclaimer of claim scope made in the parentapplication or any predecessor application in relation to the instantapplication. The Examiner is therefore advised that any such previousdisclaimer and the cited references that it was made to avoid, may needto be revisited. Further, any disclaimer made in the instant applicationshould not be read into or against the parent application or otherrelated applications.

TECHNICAL FIELD

The present invention relates to a method and apparatus for controllinga downlink HARQ timing in a TDD environment, and more particularly, to amethod and apparatus for controlling a downlink HARQ timing of a CAsystem.

BACKGROUND ART

As communication systems have developed, various wireless terminals havebeen utilized by consumers, including companies and individuals. Acurrent mobile communication system affiliated with 3GPP (for example,LTE (Long Term Evolution), LTE-A (LTE-Advanced), and the like) may be ahigh-speed and high capacity communication system that is capable oftransmitting and receiving various data (such as image data, wirelessdata, and the like) beyond providing a sound-based service. Accordingly,there is a desire for a technology that transmits high capacity datathat is comparable to a wired communication network. Data may beefficiently transmitted through a plurality of component carriers as ascheme for transmitting high capacity data. In a TDD (Time DivisionDuplex) system, transmission (Tx) and Reception (Rx) may be executedusing a predetermined frequency band. In this instance, Tx and Rx ofdata may be executed by being distinguished based on a time slot.

Conventionally, all of the serving cells are configured based on anidentical TDD UL-DL configuration, and thus, adjustment between cellsmay not be needed. However, when different TDD configurations areconfigured for different carriers, or when a predetermined cell isconfigured as FDD and the other cell is configured as TDD, additionalhandling may be required since the TDD uplink/downlink subframe islimited in terms of time. That is, there is a desire for a method ofcontrolling a downlink HARQ timing of a CA system.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

The present invention is to control the downlink HARQ timing in a TDDenvironment.

Particularly, the present invention proposes a method of controlling thedownlink HARQ timing of an FDD/TDD CA system under the LTE-Acircumstance and an apparatus implementing the same.

Also, the present invention provides a downlink HARQ timing to beembodied in an S Cell when the duplex mode of a PCell and the duplexmode of an SCell are different, so as to reduce the feedback delay ofthe SCell.

Technical Solution

According to an embodiment of the present disclosure, there is provideda method of controlling a downlink HARQ timing, the method including:configuring, by a Base Station (BS), a duplex mode of a PCell and aduplex mode of an SCell to be different from each other, andtransmitting configuration information to a User Equipment (UE);transmitting, by the BS, a PDSCH in a subframe n-k of the SCell; andreceiving, by the BS, HARQ response information in a subframe n of thePCell from the UE by applying an association set index of a downlinkHARQ timing corresponding to the configuration information, wherein khas a value that is greater than or equal to 4 and less than or equal to13.

According to an embodiment of the present disclosure, there is provideda method of controlling a downlink HARQ timing, the method including:receiving, by a UE from a BS, configuration information that configuresa duplex mode of a PCell and a duplex mode of an SCell to be differentfrom each other; receiving, by the UE, a PDSCH in a subframe n-k of theSCell; and transmitting, by the UE, HARQ response information (HARQAcknowledgement) in a subframe n of the PCell by applying an associationset index of a downlink HARQ timing corresponding to the configurationinformation, wherein k has a value that is greater than or equal to 4and less than or equal to 13.

According to an embodiment of the present disclosure, there is provideda BS that controls a downlink HARQ timing in a TDD environment, the BSincluding: a transmitting unit that transmits information or a signal toa UE; a receiving unit that receives HARQ response information from theUE; and a controller that configures a duplex mode of a PCell and aduplex mode of an SCell to be different from each other, and controlsthe transmitting unit to transmit the configuration information to theUE, wherein the controller controls the transmitting unit to transmit aPDSCH in a subframe n-k of the SCell; and controls the receiving unit toreceive HARQ response information in a subframe n of the PCell from theUE by applying an association set index of a downlink HARQ timingcorresponding to the configuration information, and k has a value thatis greater than or equal to 4 and less than or equal to 13.

According to an embodiment of the present disclosure, there is provideda UE that controls a downlink HARQ timing in a TDD environment, the UEincluding: a receiving unit that receives, from a BS, configurationinformation that configures a duplex mode of a PCell and a duplex modeof an SCell to be different from each other, and receives a PDSCH in asubframe n-k of the SCell; a transmitting unit that transmitsinformation or a signal to the BS; and a controller that controls thetransmitting unit to transmit HARQ response information in a subframe nof the PCell by applying an association set index of a downlink HARQtiming corresponding to the configuration information, wherein k has avalue that is greater than or equal to 4 and less than or equal to 13.

Advantageous Effects

According to the present invention, in a network environment where CA issupported among serving cells configured as different duplex modes (FDDor TDD), a User Equipment (UE) may reduce a feedback delay and maytransmit downlink HARQ response information, thereby improving theperformance of a system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a CA (Carrier Aggregation) deployment scenarioaccording to an embodiment of the present invention;

FIG. 2 illustrates a TDD-FDD CA scenario;

FIG. 3 is a diagram illustrating a TDD-FDD CA scenario to which anembodiment of the present invention is applicable;

FIG. 4 is a diagram illustrating a HARQ response information feedbackunder a TDD-FDD CA configuration;

FIGS. 5 to 11 are diagrams illustrating a downlink association set whenthe duplex mode of a PCell is a TDD mode and the duplex mode of an SCellis an FDD mode according to an embodiment of the present invention;

FIG. 12 illustrates a legacy DL HARQ timing;

FIG. 13 is a diagram illustrating a HARQ timing when the duplex mode ofa PCell is an FDD mode and the duplex mode of an SCell is a TDD modeaccording to an embodiment of the present invention;

FIG. 14 is a diagram illustrating operations executed between a BaseStation (BS) and a User Equipment (UE) according to an embodiment of thepresent invention;

FIG. 15 is a diagram illustrating a process in which a BS controls adownlink HARQ timing in a TDD environment, according to an embodiment ofthe present invention;

FIG. 16 is a diagram illustrating a process in which a UE controls adownlink HARQ timing in a TDD environment, according to an embodiment ofthe present invention;

FIG. 17 is a diagram illustrating a configuration of a BS that controlsa downlink HARQ timing in a TDD environment, according to an embodimentof the present invention; and

FIG. 18 is a diagram illustrating a configuration of a UE that controlsa downlink HARQ timing in a TDD environment, according to an embodimentof the present invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. In the followingdescription, the same components will be designated by the samereference numerals although they are shown in different drawings.Further, in the following description of the present invention, adetailed description of known functions and configurations incorporatedherein will be omitted when it may make the subject matter of thepresent invention rather unclear.

The wireless communication system may include a User Equipment (UE) anda Base Station (BS or an eNB). Throughout the specifications, the userequipment may be an inclusive concept indicating a user terminalutilized in wireless communication, including a UE (User Equipment) inWCDMA, LTE, HSPA, and the like, and an MS (Mobile station), a UT (UserTerminal), an SS (Subscriber Station), a wireless device, and the likein GSM.

The base station or a cell, may generally refer to a station wherecommunication with the user equipment is performed, and may also bereferred to as a Node-B, an eNB (evolved Node-B), a Sector, a Site, aBTS (Base Transceiver System), an Access Point, a Relay Node, and thelike.

That is, the base station or the cell may be construed as an inclusiveconcept indicating a portion of an area covered by a BSC (Base StationController) in CDMA, a NodeB in WCDMA, an eNB or a sector (site) in LTE,and the like, and the concept may include various coverage areas, suchas a megacell, a macrocell, a microcell, a picocell, a femtocell, acommunication range of a relay node, and the like.

In the specification, the user equipment and the base station are usedas two (uplink or downlink) inclusive transceiving subjects to embodythe technology and technical concepts described in the specifications,and may not be limited to a predetermined term or word.

In a system, such as LTE and LTE-A, to which the present invention maybe applied, a standard may be developed by configuring an uplink and adownlink based on a single carrier or a pair of carriers. The uplink andthe downlink may transmit control information through a control channel,such as a PDCCH (Physical Downlink Control CHannel), a PCFICH (PhysicalControl Format Indicator CHannel), a PITCH (Physical Hybrid ARQIndicator CHannel), a PUCCH (Physical Uplink Control CHannel), and thelike, and may be configured as a data channel, such as a PDSCH (PhysicalDownlink Shared CHannel), a PUSCH (Physical Uplink Shared CHannel), andthe like, so as to transmit data.

The abbreviations that are used throughout the present specificationwill be described as follows:

PCell: Primal)/serving cell

SCell: Secondary serving cell

Uplink transmission and downlink transmission may be performed based ona TDD (Time Division Duplex) scheme that performs transmission based ondifferent times, or based on an FDD (Frequency Division Duplex) schemethat performs transmission based on different frequencies. Meanwhile, atimepoint of a downlink and a timepoint of an uplink may bedistinguished in TDD, and when various TDD configurations exist,timepoints may be varied.

Table 1 provided below shows TDD configurations. It shows that the UL-DLsubframe transmission timing is different for each TDD configuration.

TABLE 1 Uplink-downlink configurations Uplink- Downlink- downlinkto-Uplink config- Switch-point Subframe number uration periodicity 0 1 23 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5ms D S U D D D S U D D 3 10 ms  D S U U U D D D D D 4 10 ms  D S U U D DD D D D 5 10 ms  D S U D D D D D D D 6 5 ms D S U U U D S U U D

In Table 1, in a radio frame corresponding to 10 subframes, a regionmarked with D denotes a downlink and a region marked with U denotes anuplink. S denotes a special subframe that is switched from a downlink toan uplink (Downlink-to-Uplink Switch-point periodicity).

Table 2 shows a downlink association set index K in a TDD mode. K is{k₀, k₁, . . . , k_(M-1)}.

TABLE 2 Downlink association set index K: {k₀, k₁, . . . , k_(M−1)}, inTDD UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 — — 6— 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, 4, 6 — —3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 11 6, 5, 4, 7 — — — —— — 5 — — 13, 12, 9, 8, — — — — — — — 7, 5, 4, 11, 6 6 — — 7 7 5 — — 7 7—

Based on a UL-DL configuration, an uplink subframe that is associatedwith a downlink subframe may be changed. For example, according to UL-DLconfiguration #3, a subframe 2 is an uplink subframe and is associatedwith downlink subframes that are received 7, 6, and 11 subframes beforethe uplink subframe 2. ACK/NACK information with respect to the downlinksubframes that are received 7, 6, and 11 subframes before the uplinksubframe 2 may be transmitted through the uplink subframe 2. When one ofthe TDD UL-DL configurations is used, a User Equipment (UE) may beaware, in advance, of whether a downlink or an uplink is to be used at acorresponding timepoint. The information enables the UE to execute aprediction and to operate.

In all of the UL subframes (UL subframe n) of a UE that is configuredwith FDD, HARQ response information (HARQ acknowledgement) with respectto a DL subframe n−4, which is transmitted k=4 subframes before the ULsubframe n, may be transmitted. Hereinafter, a UL subframe through whichHARQ response information with respect to a DL subframe is transmitted,may be referred to as a UL subframe associated with the DL subframe.

Also, the HARQ response information takes a HARQ-ACK as an example, andhas one of ACK and NACK through HARQ as a value. Alternatively,according to an embodiment, the HARQ response information may have athird value in addition to ACK and NACK

FIG. 1 illustrates a CA (Carrier Aggregation) deployment scenarioaccording to an embodiment of the present invention.

The diagram 110 shows that F1 and F2 coexist and overlap, and providealmost the same coverage. F1 and F2 indicate carrier frequency bands.The two layers may provide sufficient coverage and mobility, and F1 andF2 may be formed of an identical band.

The diagram 120 shows that F1 and F2 coexist and overlap, and F2provides a relatively smaller coverage due to a path loss. F1 provides asufficient coverage, and F2 improves throughput. F1 and F2 may be formedof different bands than each other.

The diagram 130 shows that F1 and F2 coexist, and an F2 antenna islocated in the cell boundary of F1, thereby improving the throughput ofthe cell boundary. F1 and F2 may be formed of different bands than eachother.

The diagram 140 shows that F1 provides macro coverage, and F2 uses anRRH and improves the throughput as being a hotspot. F1 and F2 may beformed of different bands than each other. An F2-based RRH may becombined with an F1 macro cell.

The diagram 150 is similar to the diagram 120, but shows an example inwhich a frequency selective repeater is deployed and the coverage isenlarged. F1 and F2 may be aggregated so that the coverages overlap byan identical eNB.

The case in which frequency bands F1 and F2 operate based on differentduplex modes in the CA (for example, the case in which one frequencyband operates based on TDD and the other frequency band operates basedon FDD) is referred to as a TDD-FDD CA.

FIG. 2 illustrates a TDD-FDD CA scenario.

In FIG. 2, operations should be possible based on CA scenarios 1 to 4110, 120, 130, and 140 of FIG. 1. Any one of FDD and TDD may serve as aPCell. Although a network is capable of supporting TDD-FDD CA, thelegacy FDD UEs may camp on a single FDD

Also, although the network is capable of supporting TDD-FDD CA, thelegacy TDD UEs may camp on a single TDD cell.

FIG. 3 is a diagram illustrating a TDD-FDD CA scenario to which anembodiment of the present invention is applicable.

In the scenario shown in FIG. 3, a macro operates based on TDD in an f1carrier 316 and 354, and a small cell operates based on FDD in an f2carrier 312, 314, and 352. The opposite scenario (for example, the casein which the macro operates based on FDD (f1) and the small celloperates based on TDD (f2)) may also be considered. Here, the macro andthe small cell are based on an ideal backhaul 301, and may be consideredas an environment similar to CA scenario #4. Also, it is assumed that aPUCCH transmission of a HARQ (Hybrid Automatic Retransmit reQuest)Acknowledgement/Negative Acknowledgement (A/N) transmission with respectto a DL PDSCH transmission is transmitted in a PCell as usual.

In the scenario, the situation in which a TDD-FDD CA UE is configuredwith CIF or not may be additionally considered.

FIG. 4 is a diagram illustrating a HARQ response information feedbackunder a TDD-FDD CA configuration.

FIG. 4 illustrates that an additional consideration is required inassociation with a DL HARQ transmission in a deployment environment inwhich a PCell is configured with TDD and an SCell is configured withFDD. For example, a large number of DL subframes of an FDD SCC cell arenot capable of supporting HARQ A/N bits based on an existing FDD DL HARQtiming in a UL subframe of the PCell configured with TDD. Therefore, anadditional consideration is required in association with the abovedrawback.

Accordingly, the present specification suggests a DL association setpreferred by an SCC FDD based on each PCC_TDD UL-DL configuration bytaking into consideration a feedback delay, a load balancing of feedbackbits, support of peak data rate, standard impact, or the like whendetermining a timing.

FIGS. 5 to 11 are diagrams illustrating a downlink association set whenthe duplex mode of a PCell is a TDD mode and the duplex mode of an SCellis an FDD mode according to an embodiment of the present invention.

Hereinafter, unlike a PCC_TDD, an SCC_FDD in FIGS. 5 to 11 needs totransmit A/N with respect to all PDSCH transmissions executed in anSCell, in a TDD UL subframe corresponding to the PCell, since DL/UL aresimultaneously executed in all subframes. Therefore, the TDD of thePCell may operate based on a DL HARQ timing that is appropriate for acorresponding TDD UL-DL configuration, and a plurality of followingmethods may be used for FDD. P that includes a pattern of horizontalsolid line indicates a subframe through which A/N is transmitted in aPCell (e.g., PUCCH). D indicates a PDSCH. P marked on an SCell is forreference, and A/N transmission is actually executed in a PCell ULsubframe.

FIG. 5 shows a downlink association set when a PCell (PCC) has TDDconfiguration #0 and an SCell (SCC) is configured with FDD, according toan embodiment of the present invention. In association with the PCellhaving TDD configuration #0, four schemes may exist, which are A0_1,A0_2, A0_3, and A0_4.

In addition to A0_1 and A0_2 downlink association sets as shown in FIG.5, the case that may create an effect greater than or equal to the TDDperformance of Table 2 out of all downlink association sets that can bedrawn from the TDD configuration #0 of the PCell will be described asfollows.

TABLE 3 Candidates of a downlink association set index when the UL-DLconfiguration of a PCell is 0 UL-DL configuration Subframe n (FDD,SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 0 A0_1 — — 6, 5, 4 4 4 — — 6, 5,4 4 4 A0_2 — — 6, 5 5, 4 4 — — 6, 5 5, 4 4 A0_3 — — 6 6, 5 5, 4 — — 6 6,5 5, 4 A0_4 — — 6, 5, 4 — 5, 4 — — 6, 5, 4 — 5, 4

FIG. 6 shows a downlink association set when a PCell (PCC) has TDDconfiguration #1 and an SCell (SCC) is configured with FDD, according toan embodiment of the present invention. In association with the PCellhaving TDD configuration #1, four schemes may exist, which are A1_1,A1_2, A1_3, and A1_4.

In addition to A1_1, A1_2, A1_3 downlink association sets as shown inFIG. 6, the case that may create an effect greater than or equal to theTDD performance of Table 2 out of all downlink association sets that canbe drawn from the TDD configuration #1 of the PCell will be described asfollows.

TABLE 4 Candidates of a downlink association set index when the UL-DLconfiguration of a PCell is 1 UL-DL configuration Subframe n (FDD,SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 1 A1_1 — — 7, 6, 5, 4 4 — — — 7,6, 5, 4 4 — A1_2 — — 7, 6, 5 5, 4 — — — 7, 6, 5 5, 4 — A1_3 — — 7, 6 6,5, 4 — — — 7, 6 6, 5, 4 — A1_4 — — 7 7, 6, 5, 4 — — — 7, 7, 6, 5, 4 —

FIG. 7 shows a downlink association set when a PCell (PCC) has TDDconfiguration #2 and an SCell (SCC) is configured with FDD, according toan embodiment of the present invention. In association with a PCell thathas TDD configuration #2, one scheme (A2_1) may exist.

TABLE 5 Candidates of a downlink association set index when the UL-DLconfiguration of a PCell is 2 (A2_1) UL-DL configuration Subframe n(FDD, SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 2 — — 8, 7, 6, — — — — 8,7, 6, — — 5, 4 5, 4

FIG. 8 shows a downlink association set when a PCell (PCC) has TDDconfiguration #3 and an SCell (SCC) is configured with FDD, according toan embodiment of the present invention. Seven schemes (A3_1, A3_2, A3_3,A3_4, A3_5, A3_6, and A3_7) are provided out of various possibleexamples in association with a PCell having TDD configuration #3.

In addition to the downlink association sets as shown in FIG. 8, thecase that may create an effect greater than or equal to the TDDperformance of Table 2 out of all downlink association sets that can bedrawn from the TDD configuration #3 of the PCell will be described asfollows.

TABLE 6 Candidates of a downlink association set index when the UL-DLconfiguration of a PCell is 3 UL-DL configuration Subframe n (FDD,SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 3 A3_1 — — 11, 10, 9, 8, 7, 6 6,5 5, 4 — — — — — A3_2 — — 11, 10, 7, 6 10, 6, 5 10, 5, 4 — — — — — A3_3— — 11, 7, 6 11, 10, 6, 5 10, 5, 4 — — — — — A3_4 — — 11, 7, 6 11, 6, 511, 10, 5, 4 — — — — — A3_5 — — 11, 10, 9, 8 8, 7, 6 6, 5, 4 — — — — —A3_6 — — 11, 10, 9 9, 8, 7, 6 6, 5, 4 — — — — — A3_7 — — 11, 10, 9 9, 8,7 7, 6, 5, 4 — — — — — A3_8 — — 11, 10, 9, 8, 7 7, 6, 5 5, 4 A3_9 — —11, 10, 9, 8 8, 7, 6, 5 5, 4 — — — — — A3_10 — — 11, 9, 8, 6 11, 8, 6 6,5, 4 — — — — — A3_11 — — 11, 10, 7, 6 10, 9, 6, 5 5, 4 — — — — — A3_12 —— 11, 10 10, 9, 8, 7 7, 6, 5, 4 — — — — —

Some of the examples are only disclosed, in which HARQ with respect to10 downlink subframes are distributed to uplink subframes when the UL-DLconfiguration of a PCell is 3. In addition to the examples shown inTable 6, when a subframe n is 2, 3, or 4, values from 4 to 11 may beallocated as candidates of a downlink association set by taking intoconsideration a feedback delay. As a matter of course, a value that isgreater than 11 may be allocated. However, this may cause a feedbackdelay in some subframes, and thus, design may be executed by taking intoconsideration the same.

FIG. 9 shows a downlink association set when a PCell (PCC) has TDDconfiguration #4 and an SCell (SCC) is configured with FDD, according toan embodiment of the present invention. In association with a PCellhaving TDD configuration #4, five schemes (A4_1, A4_2, A4_3, A4_4, A4_5,A4_6, and A4_7) may exist.

In addition to the downlink association sets as shown in FIG. 9, thecase that may create an effect greater than or equal to the TDDperformance of Table 2 out of all downlink association sets that can bedrawn from the TDD configuration #4 of the PCell will be described asfollows.

TABLE 7 Candidates of a downlink association set index when the UL-DLconfiguration of a PCell is 4 UL-DL configuration Subframe n (FDD,SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 4 A4_1 — — 12, 11, 10, 9, 8, 77, 6, 5, 4 — — — — — — A4_2 — — 12, 11, 10, 8, 7 10, 7, 6, 5, 4 — — — —— — A4_3 — — 12, 11, 10, 9, 8 8, 7, 6, 5, 4 — — — — — — A4_4 — — 12, 11,9, 8, 7 11, 7, 6, 5, 4 — — — — — — A4_5 — — 12, 11, 8, 7 11, 10, 7, 6,5, 4 — — — — — — A4_6 — — 12, 11, 10, 9, 7 9, 7, 6, 5, 4 — — — — — —A4_7 — — 12, 11, 10, 7 10, 9, 7, 6, 5, 4 — — — — — — A4_8 — — 12, 10, 9,7 12, 9, 7, 6, 5, 4 — — — — — —

Some of the examples are only disclosed, in which HARQ with respect to10 downlink subframes are distributed to uplink subframes when the UL-DLconfiguration of a PCell is 4. In addition to the examples shown inTable 7, when a subframe n is 2 or 3, values from 4 to 12 may beallocated as candidates of a downlink association set by taking intoconsideration a feedback delay. As a matter of course, a value that isgreater than 12 may be allocated. However, this may cause a feedbackdelay in some subframes, and thus, design may be executed by taking intoconsideration the same.

FIG. 10 shows a downlink association set when a PCell (PCC) has TDDconfiguration #5 and an SCell (SCC) is configured with FDD, according toan embodiment of the present invention. One scheme may exist inassociation with a PCell that has TDD configuration #5.

TABLE 8 Candidates of a downlink association set index when the UL-DLconfiguration of a PCell is 5 UL-DL configuration Subframe n (FDD,SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 5 — — 13, 12, 11, 10, 9, 8, 7,6, 5, 4 — — — — — — —

FIG. 11 shows a downlink association set when a PCell (PCC) has TDDconfiguration #6 and an SCell (SCC) is configured with FDD, according toan embodiment of the present invention. In association with a PCellhaving TDD configuration #6, two schemes (A6_1 and A6_2) are provided inFIG. 11.

In addition to the downlink association sets as shown in FIG. 11, thecase that may create an effect greater than or equal to the TDDperformance of Table 2 out of all downlink association sets that can bedrawn from the TDD configuration #6 of the PCell will be described asfollows.

TABLE 9 Candidates of a downlink association set index when UL-DLconfiguration of a PCell is 6 UL-DL configuration Subframe n (FDD,SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 6 A6_1 — — 7, 6 6, 5 5, 4 — — 6,5 5, 4 — A6_2 — — 7, 5 7, 5 5 — — 7, 5, 4 7, 4 — A6_3 — — 7 7, 6 6, 5, 4— — 6, 5 5, 4 — A6_4 — — 7, 6 6, 5, 4 4 — — 6, 5 5, 4 — A6_5 — — 7, 6 6,5 5 — — 7, 5, 4 7, 4 — A6_6 — — 7, 5 7, 5 5 — — 7, 6, 5 5, 4 — A6_7 — —7, 5 7, 5 5, 4 — — 6, 4 6, 4 — A6_8 — — 7, 6 6, 5 5, 4 — — 6, 4 6, 4 —

Some of the examples are only disclosed, in which HARQ with respect to10 downlink subframes are distributed to uplink subframes when the UL-DLconfiguration of a PCell is 6. In addition to the examples shown inTable 9, when a subframe n is 2, 3, 4, 7, or 8, values from 4 to 7 maybe allocated as candidates of a downlink association set by taking intoconsideration a feedback delay. As a matter of course, a value that isgreater than 7 may be allocated. However, this may cause a feedbackdelay in some subframes, and thus, design may be executed by taking intoconsideration the same.

To sum up the descriptions that have been provided with reference toFIGS. 5 to 11 and Tables 3 to 9, a table that indicates a DL associationset index in association with a DL HARQ timing for FDD, which an eNB-UEthat has an PCell configured with TDD should comply with, may becalculated to be Table 10 as provided below.

TABLE 10 Downlink association set index K: {k₀, k₁, . . . , k_(M−1)}, inan SCell configured with FDD UL-DL configuration Subframe n (FDD, SCell)(TDD, PCell) 0 1 2 3 4 5 6 7 8 9 0 — — 6, 5 5, 4 4 — — 6, 5 5, 4 4 1 — —7, 6, 5 5, 4 — — — 7, 6, 5 5, 4 — 2 — — 8, 7, 6, 5, 4 — — — — 8, 7, 6,5, 4 — — 3 — — 11, 10, 9, 8 8, 7, 6 6, 5, 4 — — — — — 4 — — 12, 11, 10,9, 8 8, 7, 6, 5, 4 — — — — — — 5 — — 13, 12, 11, 10, 9, 8, 7, 6, 5, 4 —— — — — — — 6 — — 7, 6 6, 5 5, 4 — — 6, 5 5, 4 —

As described above, when two or more embodiments exist based on a UL-DLconfiguration of a PCell, a method that enables DL HARQ responseinformation feedback bits to be transmitted in balance in UL subframesmay be preferentially considered and may be applied as shown in Table10, which is one embodiment, and a DL association set index value may beobtained through a combination of other embodiments of other tables.

In the case of a UE that is configured with cross-carrier schedulingthrough a TDD PCell, the DL association set index as described above maybe used. However, an (E)PDCCH that transmits a DL DCI may be transmittedin a subframe earlier than a subframe n, through which a PDSCH istransmitted, by using cross-subframe scheduling, scheduling bundling, orthe like.

A DL HARQ timing for an FDD SCell when TDD is configured as a PCell hasbeen described. Hereinafter, the configuration of a DL HARQ timing foran eNB-UE that is configured with CA where FDD is configured as a PCelland TDD is configured as an SCell will be described.

Unlike the above described CA environment, UL subframes exist in all ofthe subframes of the PCell, the TDD SCell may not comply with a DL HARQtiming for each existing TDD UL-DL configuration.

FIG. 12 illustrates a legacy DL HARQ timing. FIG. 12 shows a DL HARQtiming for the existing TDD UL-DL configuration #2. In this instance, aTDD SCell does not have a problem in association with a DL HARQoperation, but an unnecessary feedback delay may occur due to a uniquecharacteristic of TDD.

FIG. 13 is a diagram illustrating a HARQ timing when the duplex mode ofa PCell is an FDD mode and the duplex mode of an SCell is a TDD mode.

FIG. 13 is a diagram illustrating an embodiment of the present inventionto reduce the feedback delay of FIG. 12.

In FIG. 13, a TDD SCell does not comply with DL association set indicescorresponding to a TDD UL-DL configuration, but applies an FDD DL HARQtiming. Therefore, all TDD UL-DL configurations apply the FDD DL HARQtiming. That is, a UE receives a PDSCH and transmits HARQ responseinformation in a PCell UL subframe after 4 ms (n+4).

When comparing the examples of FIG. 13 and FIG. 12, a UE that isconfigured with FDD (PCell)-TDD (SCell) CA supports a relatively quickerDL HARQ operation in a TDD SCell by applying the embodiment of FIG. 13,thereby improving the performance of a system.

Hereinafter, in a UE and a network that provide CA among serving cellsthat have different duplex modes (TDD-FDD CA), operations andconfigurations of the UE and a BS to which a downlink HARQ timing for anSCell is applied will be described.

FIG. 14 is a diagram illustrating operations executed between a BS and aUE according to an embodiment of the present invention. In FIG. 14, aneNB 1410 that is a BS transmits TDD-FDD CA configuration information toa UE 1420 in operation S1430. For example, a PCell may be configured asTDD and an SCell may be configured as FDD. The UE 1420 applies, to anSCell, a downlink timing corresponding to the TDD-FDD CA configurationin operation S1440. As described above, when a plurality of downlinktimings are provided in association with a single TDD-FDD CAconfiguration, a timing of a predetermined scheme may be selected. Atiming may be selected based on the duplex mode of a PCell and theduplex mode of an SCell in the TDD-FDD CA configuration.

Subsequently, the eNB 1410 transmits a PDSCH in a subframe n-k of theSCell in operation 1450. The UE calculates a subframe (n−k)+k by addinga determined k value to the subframe through which the PDSCH istransmitted based on the selected HARQ timing, and executes a HARQoperation in a subframe n of the SCell in operation S1460.

Even when CIF is configured for the UE to enable cross-carrierscheduling to be executed through the PCell, an FDD DL HARQ timing, asdescribed above, may be applied to the TDD SCell. That is, irrespectiveof whether the CIF is configured or not, under the CA as describedabove, the FDD DL HARQ timing may be equally applied to the PDSCHtransmission that is executed in all of the DL subframes of the TDDSCell.

FIG. 15 is a diagram illustrating a process in which a BS controls adownlink HARQ timing in a TDD environment, according to an embodiment ofthe present invention.

ABS configures the duplex mode of a PCell and the duplex mode of anSCell to be different from each other, and transmits configurationinformation to a UE in operation S1510. This includes theabove-described transmission of TDD-FDD CA configuration information.Subsequently, when the BS transmits a PDSCH in a subframe n-k of theSCell in operation S1520, the UE generates and transmits HARQ responseinformation with respect to the transmitted PDSCH. In this instance, thetransmission may apply the above described HARQ timing. That is, the BSapplies an association set index of a downlink HARQ timing correspondingto the configuration information, and receives, from the UE, HARQresponse information in a subframe n of the PCell in operation S1530,wherein k has a value that is greater than or equal to 4 and less thanor equal to 13. As described in FIG. 13 and the related descriptions,when the duplex mode of the PCell is an FDD mode and the duplex mode ofthe SCell is a TDD mode, k may have a value of 4. Accordingly, the HARQresponse information of the TDD SCell is transmitted at a speed that isequal to FDD. Also, when the duplex mode of the PCell is a TDD mode, andthe duplex mode of the SCell is an FDD mode, the BS receives HARQresponse information with respect to 10 consecutive downlink subframesof the SCell that are dispersively transmitted in one or more uplinksubframes in a single radio frame of the PCell. Referring to theembodiments of Table 3 to Table 10 and FIGS. 5 to 11, when the duplexmode of the PCell is a TDD mode, the number of downlink subframes ofwhich downlink association set indices are set for uplink subframes thatform a single radio frame is 10. This is applied to all of Table 3 toTable 10. That is, in the case of a conventional downlink associationset, such as Table 2, when the UL-DL configuration is 0, downlinksubframe indices that are associated with uplink subframes 2, 4, 7, and9 are 6, 4, 6, and 4. A total of 4 downlink subframes's HARQ indices areincluded. However, referring to the embodiments of Table 3 to 10 andFIGS. 5 to 11, in the case of downlink association set indices that areallocated to uplink subframes that form a single radio frame, a total of10 downlink subframe indices are matched for each configuration.

According to an embodiment of the present invention, informationassociated with a downlink association set index in an SCell that isconfigured as FDD (that is, a downlink association set index in an SCellcorresponding to the TDD configuration of a PCell) may undergo aseparate sharing process that is executed between a BS and a UE. To thisend, the BS may additionally include a process of transmitting adownlink association set index to the UE.

The downlink association set index k may be the disclosure provided inTable 3 through Table 9. Alternatively, although not disclosed in thetables, the downlink association set index k may be generated to have avalue from 4 to 13 and the embodiment thereof may be Table 10.

FIG. 16 is a diagram illustrating a process in which a UE controls adownlink HARQ timing in a TDD environment, according to an embodiment ofthe present invention.

A UE receives, from a BS, configuration information that configures theduplex mode of a PCell and the duplex mode of an SCell to be differentfrom each other, in operation S1610. This includes the above-describedreception of TDD-FDD CA configuration information. Subsequently, whenthe UE receives a PDSCH in a subframe n-k of the SCell in operationS1620, the UE generates and transmits HARQ response information (A/N)with respect to the received PDSCH. The UE applies an association setindex of a downlink HARQ timing corresponding to the configurationinformation, and transmits the HARQ response information in a subframe nof the PCell in operation 1630. In this instance, k has a value that isgreater than or equal to 4 and less than or equal to 13.

As described in FIG. 13 and the related descriptions, when the duplexmode of the PCell is an FDD mode and the duplex mode of the SCell is aTDD mode, k may have a value of 4. Accordingly, the HARQ responseinformation of the TDD SCell is transmitted at a speed that is equal toFDD.

Also, when the duplex mode of the PCell is a TDD mode, and the duplexmode of the SCell is an FDD mode, the UE dispersively transmits HARQresponse information with respect to 10 consecutive downlink subframesof the SCell in one or more uplink subframes in a single radio frame ofthe PCell. This has been described with reference to FIG. 15, and thus,the detailed descriptions thereof will be omitted.

According to an embodiment of the present invention, informationassociated with a downlink association set index in an SCell that isconfigured as FDD (that is, a downlink association set index in an SCellcorresponding to the TDD configuration of a PCell) may undergo aseparate sharing process that is executed between the BS and the UE. Tothis end, the UE may additionally include a process of receiving adownlink association set index from the BS.

The downlink association set index k may be the disclosure provided inTable 3 through Table 9. Alternatively, although not disclosed in thetables, the downlink association set index k may be generated to have avalue from 4 to 13 and the embodiment thereof may be Table 10.

FIG. 17 is a diagram illustrating a configuration of a BS that controlsa downlink HARQ timing in a TDD environment, according to an embodimentof the present invention.

The configuration of a BS 1700 includes a receiving unit 1710, acontroller 1720, and a transmitting unit 1730. The transmitting unit1730 transmits information or a signal to a UE, and the receiving unit1710 receives HARQ response information from the UE. The controller 1720configures the duplex mode of a PCell and the duplex mode of an SCell tobe different from each other, and controls the transmitting unit 1730 totransmit the configuration information to a UE. An embodiment of thetransmission of the configuration information of the duplex mode mayinclude the transmission of TDD-FDD CA configuration information. Thecontroller 1720 controls the transmitting unit 1730 to transmit a PDSCHin a subframe n-k of the SCell. The UE that receives the transmittedPDSCH may generate and transmit HARQ response information with respectto the transmitted PDSCH. In this instance, the transmission may applythe above-described HARQ timing. That is, the controller 1720 maycontrol the receiving unit 1710 to receive HARQ response informationfrom the UE in the subframe n of the PCell by applying an associationset index of a downlink HARQ timing corresponding to the configurationinformation. In this instance, k has a value that is greater than orequal to 4 and less than or equal to 13.

As described in FIG. 13 and the related descriptions, when the duplexmode of the PCell is an FDD mode and the duplex mode of the SCell is aTDD mode, k may have a value of 4. Accordingly, the HARQ responseinformation of the TDD SCell is transmitted in a speed that is equal toFDD.

Also, when the duplex mode of the PCell is a TDD mode, and the duplexmode of the SCell is an FDD mode, the receiving unit 1710 dispersivelyreceives HARQ response information with respect to 10 consecutivedownlink subframes of the SCell, in one or more uplink subframes in asingle radio frame of the PCell. Referring to the embodiments of Table 3to Table 10 and FIGS. 5 to 11, when the duplex mode of the PCell is aTDD mode, the number of downlink subframes of which downlink associationset indices are set for uplink subframes that form a single radio frameis 10. This may be applied to all of Table 3 to Table 10, and detaileddescriptions thereof will be omitted.

According to an embodiment of the present invention, informationassociated with a downlink association set index in an SCell that isconfigured as FDD (that is, a downlink association set index of an SCellcorresponding to the TDD configuration of a PCell) may undergo aseparate sharing process executed between the BS and the UE. To thisend, the transmitting unit 1730 may transmit a downlink association setindex to the UE.

The downlink association set index k may be the disclosure provided inTable 3 through Table 9. Alternatively, although not disclosed in thetables, the downlink association set index k may be generated to have avalue from 4 to 13, and the embodiment thereof may be Table 10.

FIG. 18 is a diagram illustrating a configuration of a UE that controlsa downlink HARQ timing in a TDD environment, according to an embodimentof the present invention.

The configuration of a UE 1800 includes a receiving unit 1810, acontroller 1820, and a transmitting unit 1830.

The receiving unit 1810 receives, from a BS, configuration informationthat configures the duplex mode of a PCell and the duplex mode of anSCell to be different from each other. This includes the above-describedreception of TDD-FDD CA configuration information. Also, the receivingunit 1810 receives a PDSCH in a subframe n-k of the SCell. Thetransmitting unit 1830 transmits information or a signal to the BS. Thecontroller 1820 controls the transmitting unit 1830 to transmit HARQresponse information in a subframe n of the PCell by applying anassociation set index of a downlink HARQ timing corresponding to theconfiguration information. In this instance, k has a value that isgreater than or equal to 4 and less than or equal to 13.

As described in FIG. 13 and the related descriptions, when the duplexmode of the PCell is an FDD mode and the duplex mode of the SCell is aTDD mode, k may have a value of 4. Accordingly, the HARQ responseinformation of the TDD SCell is transmitted at a speed that is equal toFDD.

Also, when the duplex mode of the PCell is a TDD mode, and the duplexmode of the SCell is an FDD mode, the controller 1820 controls thetransmitting unit 1830 to dispersively transmit HARQ responseinformation with respect to 10 consecutive downlink subframes of theSCell, in one or more uplink subframes in a single radio frame of thePCell. This has been described with reference to FIG. 15, and thus, thedetailed descriptions thereof will be omitted.

According to an embodiment of the present invention, informationassociated with a downlink association set index in an SCell that isconfigured as FDD (that is, a downlink association set index in an SCellcorresponding to the TDD configuration of a PCell) may undergo aseparate sharing process executed between the BS and the UE. To thisend, the receiving unit 1810 may receive a downlink association setindex from the BS.

The downlink association set index k may be the disclosure provided inTable 3 through Table 9. Alternatively, although not disclosed in thetables, the downlink association set index k may be generated to have avalue from 4 to 13 and the embodiment thereof may be Table 10.

By embodying a BS and a UE that have been described through FIGS. 13 to18, an effective DL HARQ timing for an SCell may be embodied in theTDD-FDD CA scenario, and the performance of the system may be improved.

An embodiment of the present invention embodies a new downlink HARQtiming that may be considered by a UE and a network that supports CAamong serving cells that are configured with different duplex modes (FDDand TDD). Particularly, an embodiment of the present invention mayimprove the performance of downlink by taking into consideration amethod for a downlink HARQ timing for an SCell. When an effective DLHARQ timing for an SCell is embodied in the TDD-FDD CA scenario, throughthe present invention, a feedback delay may be reduced in the SCell, andthus, the performance of the system may be improved.

Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims. Therefore, the embodimentsdisclosed in the present invention are intended to illustrate the scopeof the technical idea of the present invention, and the scope of thepresent invention is not limited by the embodiment. The scope of thepresent invention shall be construed on the basis of the accompanyingclaims in such a manner that all of the technical ideas included withinthe scope equivalent to the claims belong to the present invention.

1. A method of controlling a downlink HARQ (Hybrid Automatic RetransmitreQuest) timing in a CA (carrier aggregation) environment, the methodcomprising: configuring, by a base station (BS), a duplex mode of aPCell (primary cell) to be TDD (time division duplex) and a duplex modeof an SCell (secondary cell) to be FDD (frequency division duplex) andtransmitting configuration information to a user equipment (UE);transmitting, by the BS, a PDSCH (Physical Downlink Shared Channel)transmission in a subframe n−k of the SCell; and receiving, by the BS,HARQ response information associated with the PDSCH transmission in asubframe n of the PCell from the UE, by applying an association setindex k of a downlink HARQ timing associated with a UL-DL(uplink-downlink) configuration of the PCell, wherein the value of k forsubframe n for UL-DL configurations of the PCell 0, 1, 2, 3, 4, and 5 isin the table as provided below: UL-DL configuration Subframe n (FDD,SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 0 — — 6, 5 5, 4 4 — — 6, 5 5, 44 1 7, 6 6, 5, 4 — — — 7, 6 6, — 5, 4 2 — — 8, 7, 6, 5, 4 — — — — 8, 7,6, — — 5, 4 3 — — 11, 10, 9, 8, 7, 6 6, 5 5, 4 — — — — — 4 — — 12, 11,10, 9, 8, 7 7, 6, 5, 4 — — — — — — 5 — — 13, 12, 11, 10, 9, 8, 7, 6, — —— — — — — 5, 4


2. The method of claim 1, wherein cross-carrier scheduling of the PDSCHtransmission through the PCell is not enabled.
 3. The method of claim 1,wherein the PDSCH is scheduled by a downlink control information (DCI)in a (e)PDCCH (physical Downlink Control Channel).
 4. The method ofclaim 1, wherein the DL association set is a preferred DL associationset by the SCell based on a given PCell_TDD UL-DL configuration.
 5. Themethod of claim 1, wherein the configuration is a TDD-FDD CAconfiguration.
 6. The method of claim 5, wherein the UE is notconfigured with CIF.
 7. The method of claim 1, wherein the configurationinformation is transmitted on the PCell.
 8. A base station (BS) forcontrolling a downlink HARQ (Hybrid Automatic Retransmit reQuest) timingin CA (carrier aggregation) environment, comprising: a radio; and aprocessing element operably connected to the radio and configured to:configure a duplex mode of a PCell (primary cell) to be (TDD) timedivision duplex and a duplex mode of an SCell (secondary cell) to be FDD(frequency division duplex); transmit configuration information to auser equipment (UE); transmit a PDSCH (Physical Downlink Shared Channel)transmission in a subframe n−k of the SCell, wherein cross-carrierscheduling of the PDSCH transmission through the PCell is not enabled;and receive HARQ response information associated with the PDSCHtransmission in a subframe n of the PCell from the UE, by applying anassociation set index k of a downlink HARQ timing associated with aUL-DL (uplink-downlink) configuration of the PCell, wherein the value ofk for subframe n for UL-DL configurations of the PCell 0, 1, 2, 3, 4 and5 is in the table as provided below: UL-DL configuration Subframe n(FDD, SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 0 — — 6, 5 5, 4 4 — — 6, 55, 4 4 1 7, 6 6, 5, 4 — — — 7, 6 6, — 5, 4 2 — — 8, 7, 6, 5, 4 — — — —8, 7, 6, — — 5, 4 3 — — 11, 10, 9, 8, 7, 6 6, 5 5, 4 — — — — — 4 — — 12,11, 10, 9, 8, 7 7, 6, 5, 4 — — — — — — 5 — — 13, 12, 11, 10, 9, 8, 7, 6,— — — — — — — 5, 4


9. The BS of claim 8, wherein the PDSCH is scheduled by a downlinkcontrol information (DCI) in a (e)PDCCH (physical Downlink ControlChannel).
 10. The BS of claim 8, wherein the DL association set is apreferred DL association set by the SCell based on a given PCell_TDDUL-DL configuration.
 11. The BS of claim 8, wherein the configuration isa TDD-FDD CA configuration.
 12. The BS of claim 11, wherein the UE isnot configured with CIF.
 13. The BS of claim 8, wherein theconfiguration information is transmitted on the PCell.
 14. An apparatusfor controlling a downlink HARQ (Hybrid Automatic Retransmit reQuest)timing of a base station (BS) operating in a CA (carrier aggregation)environment, the apparatus comprising: a processing element configuredto cause the BS to: configure a duplex mode of a PCell (primary cell) tobe time division duplex (TDD); configure a duplex mode of an SCell(secondary cell) to be FDD (frequency division duplex); transmitconfiguration information to a user equipment (UE); transmit a PDSCH(Physical Downlink Shared Channel) transmission in a subframe n−k of theSCell; and receive HARQ response information associated with the PDSCHtransmission in a subframe n of the PCell from the UE, by applying anassociation set index k of a downlink HARQ timing associated with aUL-DL (uplink-downlink) configuration of the PCell, wherein the value ofk for subframe n for UL-DL configurations of the PCell 0, 1, 2, 3, 4 and5 is in the table as provided below: UL-DL configuration Subframe n(FDD, SCell) (TDD, PCell) 0 1 2 3 4 5 6 7 8 9 0 — — 6, 5 5, 4 4 — — 6, 55, 4 4 1 7, 6 6, 5, 4 — — — 7, 6 6, — 5, 4 2 — — 8, 7, 6, 5, 4 — — — —8, 7, 6, — — 5, 4 3 — — 11, 10, 9, 8, 7, 6 6, 5 5, 4 — — — — — 4 — — 12,11, 10, 9, 8, 7 7, 6, 5, 4 — — — — — — 5 — — 13, 12, 11, 10, 9, 8, 7, 6,— — — — — — — 5, 4


15. The apparatus of claim 14, wherein the PDSCH is scheduled by adownlink control information (DCI) in a (e)PDCCH (physical DownlinkControl Channel).
 16. The apparatus of claim 14, wherein the DLassociation set is a preferred DL association set by the SCell based ona given PCell_TDD UL-DL configuration.
 17. The apparatus of claim 14,wherein the configuration is a TDD-FDD CA configuration.
 18. Theapparatus of claim 17, wherein the UE is not configured with CIF. 19.The apparatus of claim 14, wherein the configuration information istransmitted on the PCell.
 20. The apparatus of claim 14, whereincross-carrier scheduling of the PDSCH transmission through the PCell isnot enabled